جستجوی مقالات مرتبط با کلیدواژه « Tolerance indices » در نشریات گروه « زراعت »

The water deficit is one of the most important problems in rice cultivation, particularly when the decrease in rainfall and dry season affects its vegetative growth and grain yield. Drought stress is known as one of the most effective factors of yield reduction in crops. Identifying and introducing tolerant genotypes is a good way to cope incompatible environmental conditions. For easier evaluation of genotypes under drought conditions and identification of drought tolerant genotypes, various indices have been suggested as criteria for selection of genotypes based on their yield under stress and non-stress conditions. The present study was conducted to evaluate some rice genotypes under drought stress conditions as well as to introduce drought tolerant genotypes using important tolerance and sensitivity stress indices.

This experiment was conducted in split plots based on randomized complete block design with three replications in Azadshahr, Golestan province, Iran. The main factor included two irrigation levels (drought stress and flooding as control) and the sub-factor included eight rice varieties. The experimental plots were three m2 with a distance of one m from each other. After randomly assigning the treatments to the experimental units, transplanting was done as four plants per pile. Each genotype was cultivated in six two-meter rows with a distance of 25 × 25 cm. Irrigation of the experimental field under both stress and non-stress conditions until the tillering stage of the genotypes was conducted as flooding. Then, under stressful conditions, irrigation was carried out from 40 days after transplanting (maximum tillering stage) until the end of the cropping season at an interval of 25 days, which according to the climatic conditions of the studied region, irrigation was done only once in stressful conditions. From the six rows planted in each plot, one row from around each plot was removed as border and the second to fourth rows were selected for sampling. After measuring traits and calculating different indices, the data were analyzed by SAS software. Two-dimensional biplot diagram was also drawn by STATGRAPHIC software.    
Research

The results of analysis of variance showed a significant difference between the genotypes for all studied traits under both drought stress and flooded (control) conditions. Comparison of means showed that the highest average grain yield under both control and stress conditions belonged to Fajr, IRAT216, Sang-Jo, and Sang-Tarom Gerdeh genotypes, and the lowest grain yield belonged to the Sepidrood variety. The results of the correlation coefficients showed that grain yield in control conditions had a positive and significant correlation with mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HARM), and drought tolerance (TOL) indices, respectively, and the highest correlation was observed between grain yield and MP index (r = 0.918). Also, under drought stress conditions, grain yield showed a high correlation with the harmonic mean (HARM), geometric mean productivity (GMP) and mean productivity (MP) indices, the highest of which was related to harmonic mean index (r = 0.933). The results of principal component analysis showed that 94.31% of the total variation between data was justified by the first and second principal components. Cluster analysis based on drought stress indices separated rice genotypes into three groups, and the genotypes in the first cluster had the highest drought tolerance.

The results of biplot analysis and correlation between stress indices indicated that GMP, MP, and HM indices were the best indices for selecting high-yielding genotypes under both stress and non-stress conditions in this experiment. Based on these indices and biplot diagram, Fajr, Sang-Tarom Gerdeh, Sang-Jo, and IRAT216 genotypes were identified as high-yielding and drought-tolerant genotypes, and Sepidrood and Gharib Siah Reyhani varieties as low yielding and drought sensitive genotypes.

Like other crops, wheat also faces several environmental limitations during its growth period, such as the lack of micronutrients. Zinc deficiency causes limitations in crop production, especially growth, and yield in calcareous soils. Considering the economic and agricultural importance of wheat in the world and Iran, it is necessary to pay attention to and identify genetic relationships, to know the level of genetic diversity, and estimate it in wheat germplasm by plant breeders. The present research was conducted with the aim of identifying genetic diversity and investigating stress tolerance indicators on phenological, physiological, and biochemical traits in desirable spring wheat cultivars under optimal conditions and zinc deficiency stress.

Sixty-four spring wheat cultivars under both optimal conditions and zinc deficiency stress, a simple lattice design was performed in 2019-2020 in the research farm of the Faculty of Agriculture, Urmia University. In this research, phenological traits including the number of days to germination, number of days to booting, number of days to pollination, number of days to physiological maturity, grain filling period, and physiological and biochemical characteristics including canopy temperature, total chlorophyll, leaf area index, fresh weight and dry weight, relative water content, grain protein concentration, zinc concentration in shoot and grain yield were measured.

The results of the analysis of variance revealed a significant difference among the cultivars in both optimal conditions and zinc deficiency stress in most of the studied traits. positive and significant correlations of Ys and Yp with MP, GMP, STI, and HM indices showed that these indices are the most suitable indices for screening cultivars under zinc deficiency stress conditions.

Generally, based on studied traits, tolerance indices, the results of principal components analysis, and cluster analysis, Aflak, Darya, Arvand, Roshan, Kavir, and Sirvand were selected as desirable cultivars and VEE/NAC, Tajan, Parsi, and Panjamo were identified as undesirable and susceptible cultivars. The selected tolerant and susceptible cultivars can be used for developing biparental populations, gene expression analysis, and breeding programs to produce cultivars with high yield.

Corn is an important crop that is cultivated in many parts of the world. One of the major factors limiting the plant growth is lack of water, which reduces plant growth and survival in arid and semi-arid areas. For this purpose, evaluation of the effect of drought stress on plant cultivars and identification of the tolerant genotype is of particular importance.

In this research, nine corn hybrids (including three promising hybrids H1 (SC01; TS01×MS02), H2 (KLM77021/4-1-2-1-2-4-1× K47/3), and H3 (K47/2-2-1-4-2-1-1-1× MO17) and six commercial H4 (NS640), H5 (SC703), H6 (SC704), H7 (SC720), and H9 (SC715) grain corn hybrids as late and medium maturity groups) were planted in split plots in the form of a complete random block design in three replicates at Research Unit of Moghan Agro-Industry and Livestock Company, Ardabil in spring and summer 2022. The main plots include two levels of normal irrigation (10 times of atmospheric and stack irrigation according to the region's custom) and drought stress (interruption of irrigation during the flowering and seed filling stages: eight times of atmospheric and stack irrigation so that the interruption of irrigation at the end of flowering continued to grain filling for 18 days) and the sub-plots included six varieties and three hybrids of corn. In both irrigation conditions, yield and seed yield components were evaluated. To identify the tolerant genotype based on grain yield under stress and normal conditions, stress tolerance indices (STI), stress sensitivity (SSI), tolerance (TOL), mean productivity index (MP) and geometric mean yield (GMP) were calculated. Correlation and grouping was performed based on tolerance indices of drought stress in different corn hybrids.

Dehydration stress significantly reduced the yield and yield components of corn cultivars. The H7 (SC703) and H6 (SC704) hybrids were the ones with the highest plant height, hundred seed weight, number of seed rows in cob, and number of seeds in each cob row. Further, the hybrid H1 (SC01), H6 (SC704), H7 (SC703) and H3 (K47/2-2-1-4-2-1-1-1× MO17) have the highest seed yield in both conditions of normal stress and dehydration. The correlation between grain yield and grain yield components was significant and positive. The data obtained from the evaluation of drought tolerance indices showed that there was a significant difference between different corn hybrids. As the hybrid H6 (SC704) and promising hybrid H1 (SC01) allocated the highest MP, GMP and STI, and the promising hybrid H3 (K47/2-2-1-4-2-1-1-1× MO17) showed the highest SSI value. Correlation analysis between drought tolerance indices also showed a significant positive relationship between STI, SSI, TOL, MP and GMP. The cluster analysis of the studied corn hybrids based on drought tolerance indices divided the corn hybrids into three separate groups, such that the hybrids H1 (SC01), H3 (K47/2-2-1-4-2-1-1-1× MO17), H6 (SC704) and H7 (SC703) were classified as drought tolerant hybrids within the same group.

It seems that by simultaneous trait evaluation of the grain yield and grain yield components along with drought tolerance indices, it is possible to identify the genotype with high grain yield under water deficit stress. The information acquired by the study might be applied in the future remedial programs.

Vernalization genes (Vrn), in addition to controlling the growth habit of wheat (spring and winter), play a key role in flowering time and early maturity of wheat. They are also of great interest in drought tolerance researches. To investigate the effect of Vrn genes on drought tolerance, four isogenic lines were developed. Isogenic lines were resulted from the crosses of the early heading Australian variety, Excalibur, with the late heading Iranian variety, Roshan, and followed by backcrossing with Roshan. Two experiments were conducted based on randomized complete block design with four replications under rainfed conditions of Sepidan during 2019-2020 and under well-watered conditions of Kerman during 2020-2021 cropping years. In the present research, seven important agronomic traits, including days to heading, days to ripening, grain filling period, spike number per meter square, grain number per spike, 1000-grain weight, and grain yield were assessed. Isogenic lines were assessed for drought tolerance using eight indices, including mean of productivity (MP), yield index (YI), stress tolerance index (STI ), geometric mean of productivity (GMP), stress susceptibility index (SSI ), yield stability index (YSI), and stress tolerance score (STS). The results of stress tolerance score (STS) showed that isogenic lines vrn-B1/Vrn-D1a and Vrn-B1a/vrn-D1 had the highest and the lowest stress tolerance score, respectively. In addition, the vrn-B1 and Vrn-D1a alleles, which cause early flowering, improve drought tolerance by utilizing an escape mechanism from dry conditions.

In order to evaluate the tolerance to water deficit stress in bread wheat genotypes, 144 genotypes in square lattice with two replications and in two modes of supplementary and water deficit irrigation were evaluated in the rainfed research station of Zanjan Agricultural Research Center during the 2016-2017 crop year. Based on grain yield under supplementary and water deficit irrigation conditions, different stress tolerance indices were measured. The results of analysis of variance showed the existence of genetic diversity between the studied genotypes based on water stress tolerance indices. Comparison of mean genotypes in terms of yield in supplementary and water deficit irrigation conditions showed that 82, 101, 116, 13, 86, 131 and 65 have the highest yield in both environmental conditions. Based on STI, MP, GMP and HM indices, G88 and based on TOL, SSI and YSI indices, G41 genotype were identified as tolerant genotypes. Apart from SSI and YSI indices, other studied indices had a significant correlation with environmental performance and therefore can be used effectively to select cultivars tolerant to drought stress. Using bi-plot diagrams obtained from analysis to the main components, genotype tolerance indices were divided into two separate groups. The genotypes identified by STI, MP, GMP and HM indices were grouped and the genotypes identified by TOL, SSI and YSI indices were placed in a separate group. The genotypes identified in this study can be used in future breeding programs of bread wheat to tolerate water deficit stress in the region.

Drought is one of the most important factors limiting the environment for plant growth and productivity, especially in the flowering and filling stages of barley. A study was conducted to compare some statistical methods and different indicators of stress tolerance with the aim of introducing an ideal method for selecting drought tolerant lines. After wheat, barley is one of the most important crops. Barley is the fourth cereal crop in the world after wheat, corn and rice. One of the factors affecting the production of plants is water defecit, and barley has more efficient mechanisms against water shortage than other grains. Because it has higher relative drought tolerance compared to other grains. In these arid and semi-arid regions like Iran, the presence of drought stress during plant growth is a natural problem.

In this study, 18 diverse barley lines at two water levels (normal conditions and water deficit stress) were examined. This experiment was performed as a randomized complete block design with three replications at the Seed and Plant Improvement Research Institute of Karaj, Iran in 2020. Drought tolerance and susceptibility indices were assessed. These indices included stress sensitivity index, mean productivity, tolerance, stress tolerance index, geometric mean productivity, harmonic mean productivity, performance under stress conditions (Ys) and normal (Yp) conditions. Correlation coefficient between yield in drought and irrigation conditions and other stress indicators was estimated according to statistical techniques. Correlation between indices and grain yield under stress and normal conditions was calculated using Minitab software. Selection based on multiple traits in breeding programs is likely to be effective in improving grain yield under drought stress conditions. The purpose of this study is to identify the most suitable indicators and compare different stress tolerance indicators to select high-yielding and drought-tolerant lines and to identify the superior barley line.

The highest GMP and MP were related to 4 and 13 lines. Based on tolerance index (TOL), genotype 1 had the lowest and line 7 showed the highest level of tolerance, respectively. Based on MP and GMP indices, 4, 7 and 13 lines had high drought tolerance. A high positive and significant correlation was observed between MP, GMP, Ys, Yp, which indicates that these indices are suitable for identifying drought tolerant lines. Based on the results of the principal component analysis and the bi-plot diagram, it was observed that the lines tolerant to drought stress are almost consistent with the clustering pattern of tolerant lines and the lines sensitive to drought stress are also consistent with the clustering of sensitive lines. MP and GMP indices are suitable for evaluating drought tolerance because they showed a high correlation with grain yield under normal conditions and under water stress. The closeness of 4 and 13 lines to GMP, MP, HARM, Ys indicates the tolerance of these lines to drought stress and therefore they can be suggested as drought tolerant lines.

Selection of drought tolerant lines based on a combination of tolerance indices can provide useful criteria for drought tolerance. A high positive and significant correlation was observed between MP, GMP, Ys, Yp, which indicates that these indices are suitable for identifying drought tolerant lines. These results help the modifier to select lines in different environments. Principal component analysis showed that it is important to introduce genotypes with desirable traits such as genotypes with high yield and resistance to drought stress. It is possible to speed up the improvement of new barley cultivars by using stress tolerance indicators by breeders. In general, 4, 7, and 13 lines were drought tolerant and can be used for barley improvement programs. Based on principal component analysis, drought sensitive and tolerant lines were consistent with cluster analysis. Exploiting the results of the present study can help breeders to select and identify genotypes that have relative tolerance to drought stress.

Chickpea is mainly grown in the west and north west of Iran in dryland conditions, and in most areas, it is planted as post rainy season crop from March to late May. Due to irregular, untimely and insufficient rainfall in cultivated areas, this plant is usually suffering from drought during flowering and pod filling stages, which are the most susceptible stages of chickpea growth. Utilization of local genetic diversity that are useful sources of adaptation gene to environmental changes is a starting point and a functional approach to overcome this problem. Assuming the local chickpea accession conserved in National Plant Gene Bank of Iran (NPGBI) have appropriate diversity for terminal drought tolerance, a research was conducted with the aim of identify drought tolerant accessions and determining their yield potential under dryland condition.

Seventy Kabuli chickpea landraces were identified as tolerant accessions in different previous projects were done in NPGBI entered to this study. The experiment was held in Sanandaj and Karaj research station both in two different treatments. Control and drought treatments, through cutting off irrigation at flowering stage till maturity, in Karaj and dryland and complementary irrigation treatments, using two additional irrigations during flowering and pod filling, in Sanandaj station. The accessions were planted in the second half of March in augmented design, during 2016-17 growing season. Different agronomical traits were recorded, quantitative drought tolerance and susceptibility indices, were calculated and based of them accessions were grouped using the principle component and cluster analysis.

 Based on the results, a significant decrease in day to maturity, flowering period, canopy height and width, plant weight, pods number and weight per plant, seeds number per plant, plant yield, biomass, yield and harvest index were observed in drought stress conditions. There was considerable variation in yield and yield components, biomass and harvest index, among understudied landraces. Seed production increased by 9.7 and 1.3 times under irrigation treatment in Karaj and Sanandaj, respectively.Principal component analysis across tolerant and susceptible indices and considering eigen values greater than or equal to 1.0 showed that in both locations, two components together accounted for 92.32 and 99.33 percent of variation. The first component contributed most of the variability 52.18% in Karaj and 83.62% in Sanandaj was explained by variation in HM, STI, GMP and MP indices. The second component was explained by the diversity among genotypes for TOL and SSI indices. Hence, accession number KC.215172, KC.215286, KC215369 and KC.216010 in Sanandaj station and accession number KC.215286, KC.215727, KC215442, KC.215443, and KC.216023 in Karaj with higher amount of GMP and STI indices and lower amount of TOL and SSI were among more drought tolerance accessions.Cluster analysis based on evaluated traits and calculated drought tolerance and susceptibility indices, were divided accessions in to 3 clusters in Karaj. The cluster number three that TOl and SSI indices and the percentage of unfilled pods had lower values than the total average and plant weight, seed and pod number per plant, seed and pod weight per plant, biomass, yield, harvest index and STI and GMP indices have higher values than the average was called drought tolerant cluster. Accessions number KC.215727, KC.215442, KC.215710, KC.216023 were this cluster member.  The cluster number 4 that had high yield potential and high STI and GMP indices and including 24 accessions was drought tolerant cluster in Sanandaj. Accession number KC215369 was in this group.

Although it is possible to increase the yield of chickpea by changing the planting season from traditional spring planting to winter, but farmers still prefer spring planting. Therefore, it is necessary to produce suitable high-yielding cultivars for both seasons, because in this way, farmers have the opportunity to choose suitable cultivars for spring or winter planting, depending on their local environmental or climatic conditions. The mismatch between grouping of tolerant genetic accessions in two experimental locations was due to the lack of similarity of stress intensities between two locations. The intensity of stress was 0.89 in Karaj and 0.24 in Sanandaj and this issue affects the reaction of the accessions. Genotype × environment interaction is the most important challenge in breeding program. Therefore, description of interaction effects and finding out appropriate genotypes with specific or common adaptation for target environments is the most important aim for multi-year and multi-location assessments. Summarizing the results of both sites demonstrated accessions number KC.215286, KC.215442 and KC.215443 were superior genotypes at both locations.Totally, this study revealed the existence of desirable diversity in terms of agronomic traits and stress tolerance among local accessions of chickpea and highlighted the importance of paying attention to these accessions for advanced and complementary research to identify potentials of these valuable heritage.

Drought stress is one of the most important factors in reducing yield and barley production in rainfed arid regions, and counteracting or reducing the effect of stresses as a useful solution to increase barley yield. Therefore, improvement of stress-tolerant and suitable barley cultivars for arid and semi-arid regions is essential.

In order to evaluate drought tolerance of 121 genotypes, lines and barley cultivars and identify tolerant and susceptible genotypes based on grain yield and drought tolerance indices, an experiment in a randomized complete block design with two replications in Maragheh rainfed agricultural research station was carried out in rainfed and irrigated conditions during the cropping years of 1394-94 and 1394-95. Evaluated traits included spikes number, seeds numder, 1000-seed weight, days to heading, days to maturity and grain yield.

The results of correlation between drought tolerance indices and grain yield in rainfed and irrigated conditions showed that tolerance index (STI), mean productivity (MP), harmonic mean (HM) and geometric mean productivity (GMP) were positively correlated, and had significance with grain yield traits in both environmental conditions. So, they were suitable indicators for selecting high yielding cultivars in both rainfed and irrigated environments. Also, the number of fertile spikes and 1000-seed weight had a significant correlation with STI, GMP, MP and HM indices in both conditions. In the principal components analysis based on drought tolerance index and grain yield under water conditions, the three components together accounted for 81% of the diversity of the initial data. In rainfed conditions, the three components described about 88% of the total diversity.

In this study, genotypes 10 (71557), 100 (Tokak / Demir-2) and 38 (72480) in both rainfed and irrigated environments showed higher grain production potential than other genotypes.

Water stress is one of the most important challenges that the plant faces. Regarding the importance of drought stress and its effect on plant yield, 12 oilseed sunflower genotypes under normal and drought stress conditions were evaluated in the year 2016. In conditions of normal and drought stress, genotypes of Progress and Sor had the highest grain yield potential respectively. 11 tolerance and stress susceptibility indices were calculated based on grain yield in non-stress and drought stress conditions. The MP, GMP, STI, Harm, YI and DI indices were used due to positive and significant correlation with grain yield under both normal and stress conditions for identification and selection of tolerant and sensitive drought stress genotypes. The first two components of the analysis of the main components of the studied indices and grain yield in both conditions justifies more than 99% of the variation. The coefficients of the analysis of the main components of the indices, the first component was named as the component of grain yield potential and drought stress tolerance and the second component as a component of drought stress susceptibility. Cluster analysis based on the values of first and second components derived from drought stress indices, classified genotypes into five independent groups. The genotypes used in this study showed high genetic diversity in drought stress. Finally, the Progress and Sor genotypes were the most tolerant and the Lakomka genotype was the most sensitive genotype for the end of season drought stress.

Phosphorus is one of the essential elements in plants. In calcareous soils, the amount of available phosphorus is very low due to high pH, excessive levels of calcium carbonate, lack of organic matters, and also the insolubility of phosphate minerals under such conditions. Since a large amount of phosphorus fertilizer is constantly applied to the calcareous soils of Iran, identification of genotypes with efficient phosphorus uptake may help farmers to manage the application of chemical fertilizers. Phosphorus uptake efficient genotypes can be identified using different indices including tolerance index (TOL), mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI; Fernandez, 1992), abiotic tolerance index (ATI; Moosavi et al., 2008), stress susceptibility index (SSI), drought index (DI), harmonic mean (HARM) and modified stress tolerance indices (kiSTI_K1S and K2STI; Naderi et al., 2008). This study was conducted to screen tolerant oilseed sunflower pure lines for phosphorus deficiency stress with higher and efficient phosphorus uptake to develop an improved genetic population for farmers’ usage.

Ninety-five oilseed sunflower pure lines were evaluated using a randomized complete block design with three replications under both optimal and deficiency conditions of absorbable phosphorus at the Urmia University research field during the 2015-2016 cropping season. This experiment was conducted in 15 kg plastic pots. Soil phosphorus concentration in phosphorus deficiency treatment was 7.240 mg.kg-1 while under optimal condition, 0.4 g.kg-1 of triple superphosphate were added. Tolerance indices were calculated for the sunflower lines based on the grain yield under optimal and deficiency conditions of absorbable phosphorus. In order to find suitable indices for screening the tolerant lines, a simple correlation coefficient was performed between the calculated tolerance indices and grain yield under optimal and deficiency conditions of phosphorus. Principal components analysis (PCA) and cluster analysis were performed to evaluate the relationship between the tolerance indices and the studied genotypes and to select the most desirable and tolerant lines.

Results illustrated that phosphorus deficiency reduced the grain yield of all genotypes and mean grain yield in phosphorus deficiency conditions was 44.88% lower than that in optimal conditions which indicates the importance of phosphorus on sunflower grain yield. The result of correlation analysis revealed a highly significant correlation between HARM, MP, GMP, and STI indices with grain yield under optimal and deficiency conditions of phosphorus. Therefore, these indices could be considered as the most suitable indices for screening tolerant lines to phosphorus deficiency conditions which also showed higher grain yield under optimal and deficiency conditions of phosphorus. Principal component analysis (PCA) showed that the first three components accounted for 94.5% of the total variation, with principal component (PC) 1 accounting for 63.1%, PC2 for 21.6% and PC3 for 9.8% of the total variation. The heatmap hierarchical clustering indicated that all the lines were clustered into three major groups, with cluster 1 (6 lines) being, in general, drought-tolerant followed by cluster 2 (29 lines) whereas, cluster 3 (60 lines) being drought-sensitive. The results of principal component and cluster analysis based on stress tolerance indices indicated that the lines 38, 94, and 95 not only showed higher tolerance in terms of tolerance indices but also they produced relatively high grain yield and had higher total phosphorus absorption values under both optimal and deficiency conditions of phosphorus, which indicated their uptake efficiency and efficient use of soil phosphorus. The results obtained from all the applied methods revealed that the lines 38 (Yp=72.23; Ys=54.37; TAPp=400.53; TAPs=106.40), 94 (Yp=70.60; Ys=34.73; TAPp=121.93; TAPs=44.00), and 95 (Yp=70.67; Ys=25.77; TAPp=36.53; TAPs=21.53) are the most desirable and tolerant ones. Therefore, these lines can be used in breeding programs to introduce new phosphorus efficient varieties with high grain yield.

In order to evaluate durum wheat lines in terms of frost stress tolerance, 45 promising durum wheat lines resulting from crosses between different parents were assessed using stress tolerance indices. This experiment consisting of greenhouse and laboratory tests was performed in the Faculty of Plant Breeding of MohagheghArdabili University in the 2017-18 crop year. In this experiment, wheat lines at seedling stage were studied. Durum wheat lines were planted in a factorial design based on randomized complete blocks with three replications. Plants up to 3 to 5 leaf stage were kept in greenhouse conditions. The pots were then taken to a cold room at 4°C to prepare for stress. Based on biological performance, tolerance indices (TOL), stress sensitivity (SI), average production (MP), stress tolerance index (STI) Geometric mean of production (GMP), Harmonic mean of production index (HARM), Yield reduction index (Yr) and Root and shoot tolerance index (TI) were calculated. The results of analysis of variance showed that the studied lines had significant differences in terms of MP, GMP and HARM traits and Yr and Ti indices were significant in stress. The interaction of the line in stress was insignificant for all indices. Due to the correlation between performance and indices, the most appropriate indices were MP, GMP, HARM and TOL. Comparison of mean lines and stresses were examined separately. The maximum correlation coefficient was related to the relationship (0.999) between STI index with SI, Yr with SI and Yr with STI. In general, GMP, MP and HARM indices are the most appropriate indices to evaluate the stress tolerance of lines at all levels. The study and TOL index were suitable for higher stress levels. Study of lines by indices using cluster analysis, detection function analysis and factor analysis showed similar results. The results of cluster analysis and factor analysis with the first three factors introduce lines 25, 26, 27, 28, 31, 36 and 39 as the most tolerant lines and lines 11, 13, 15, 17, 18 and 19 as the most sensitive. They were identified. In factor analysis, the first three factors explained 97.52% of the available variance and the indices of STI, SI, Yr, Ti aerial parts, MP, GMP and HARM They had the highest value and were the most effective indicators in the distribution of lines. According to the three-dimensional diagram of line distribution, the highest factor coefficients based on the first three factors were related to lines 5, 7, 25, 26, 27, 28, 31, 36 and 39.

Potato (Solanum tuberosum L.) is one of the most important crop plants in the world. Different indices have been introduced to determine stress tolerance, but in general, indices that are highly correlated with yield under both stress and non-stress conditions are considered as the best indices. Because these indices are capable of identifying high yield genotypes in both stress and non-stress environments, they can be used to estimate yield stability. Therefore, the purpose of this study was to compare different drought tolerance and susceptibility indices and group hybrids from potato cultivars in Ardabil province based on these indices.

In order to study drought tolerance indices of 12 hybrids obtained from crossover of experimental potato cultivars in a randomized complete block design with three replications at two irrigation levels (100 and 65% of plant water requirement) in Zareh Agricultural Company greenhouse Gostar Arta was performed. The first year was for genetic variation, and the second year was for greenhouse cultivation. Drought tolerance indices were also calculated for the studied genotypes in order to determine the tolerance of cultivars to different water deficit conditions. The susceptibility and stress tolerance indices (GMP, MP, STI, SSI and TOL) were used to evaluate drought tolerance and drought resistance of potato genotypes.Drought tolerance indices were calculated and after computing the indices, these indices were analyzed and compared with 100% and 65% water requirement using SPSS-22 software. Relationship between gland function in two environments and calculated tolerance indices were performed and three-dimensional graphs were plotted using SPSS-22 software. Minitab15 software was used for better evaluation of relationships by principal component analysis and biplot charts. Also, WARD method was used to select the desired hybrids for hybridization and the obtained results were obtained. A dendrogram chart form was provided. The dendrogram was plotted by Minitab15 software.

Results of analysis of variance of yield under normal conditions and 65% water use and stress tolerance indices showed variation among 12 hybrids from crosses. Under normal conditions (100% plant water requirement) the highest yield of tuber with average of 53.55 ton /h belonged to R12 hybrid (♀Luca×Esprit♂). The highest tuber yield under drought stress conditions (65% plant water requirement) was observed in S13 (♂Luca×Esprit♀) and S14 (♂Luca × Esprit♀) hybrids with 34.41 and 35.47 ton / ha, respectively. In stress conditions (65% plant water requirement) the highest tuber yield and the highest harmonic mean, geometric mean yield and stress tolerance index belonged to hybrid R14 (♀Luca × Esprit♂). The results of correlation analysis showed tuber yield under normal and stress conditions (65% of available water) and drought tolerance index, Geometric mean productivity index and average productivity index are the most appropriate indices for determining potato-tolerant hybrids. Multivariate biplot charts showed that the two hybrids R14 (♀Luca × Esprit♂) and S13 (♂Luca × Esprit♀) were adjacent to vectors related to important drought tolerance indices namely productivity mean, geometric mean productivity And stress tolerance. Also distribution of hybrids in biplot showed genetic variation among hybrids relative to drought stress. Cluster analysis showed that the highest genetic distance was between R14 (♀Luca × Esprit♂) and R12 (♀Luca×Esprit♂) hybrids and S12 (♂Luca × Esprit♀) susceptible hybrids.

Based on the results, it can be concluded that the ability of separation of drought tolerant hybrids from potato cultivars by geometric mean productivity and average productivity index and tolerance index is more appropriate and two hybrids R14 and S13 can be used as stress tolerant hybrids.

Regarding the insufficient water resources, developing of cultivars with high tolerance to water deficit can be very effective to optimize water consumption. To identify maize hybrids with higher tolerance to water deficit, 52 single cross hybrids were field evaluated according to a randomized complete block design with three replications in each irrigation regime. The hybrids were produced through crossing of 13 inbred lines from CIMMYT germplasms with four testers of A679, K166B, K18 and MO17. Two check hybrid varieties (KSC704 and KSC705) were included for comparison.  Two irrigation regimes including a normal and a deficit irrigation based on 65% water requirement of plants were applied during two growing seasons of 2014 and 2015 at the Research Station of the Agriculture and Natural Resources of Kermanshah Province. The drought tolerance and sensitive indices were calculated based on grain yield (t/ha) of hybrids at two irrigation regimes. The results of analysis of variance showed significant differences among the hybrids for grain yield and all the indices. The seed yield of hybrids in normal irrigation condition varied from 8.7 to 15.2 t/ha. This range was 4.9 to 10 t/ha in deficit irrigation condition. The cluster analysis classified the hybrids in three distinctive groups. It was recognized that hybrids number 51, 18, 45, 48, 21, 27, 23, 19, 20, 28, 38, 14 and 26 were superior than the others in terms of water deficit tolerance and grain yield. The PCA analysis showed that hybrids number 48, 45, 18 and 51 with high yield potential can be introduced as more promising ones for maize production in normal irrigation condition. However, hybrids 19, 23, 27, 25, 21, and particularly 9 were recognized more suitable for maize production in water deficit condition.

To evaluate drought tolerance in bread wheat, tritipyrum and triticale genotypes, 27 different genotypes were grown as a randomized complete block design under two irrigation regimes (control and drought) in two locations (Isfahan and Shiraz) during two growing seasons (2016 and 2017). Based on grain yield, several indices including stress tolerance index (STI), tolerance index (TOL), susceptibility index (SSI), mean productivity index (MP), geometric mean productivity index (GMP), drought sensitivity index (SDI), drought index (RDI), stress susceptibility percentage index (SSPI), Harmonic mean index (HARM) and Yield stability index (YSI) were calculated. According to the results of genotypes ranking in Isfahan region, triticale lines had the highest values of MP, GMP and STI indices over two years of study. In Shiraz region, triticale lines (4115 and 4116) had the highest values for drought tolerance indices. According to SSI and TOL indices, (triticale) and wheat genotypes (Bam, Omid and Alvand) were evaluated as drought tolerant genotypes in Isfahan region and Alvand and KaCr4 genotypes in Shiraz region in two years of evaluation. According to the correlation analyses, MP, GMP, HARM and STI indices had a positive and high correlation with grain yield in both stress and non-stress environments in both Isfahan and Shiraz regions. Superior-tolerant genotypes can be used in breeding programs to increase drought tolerance in future.

Nowadays salt tolerance of crops is becoming more and more important, owing to the constant increase of salinity in arid and semi arid regions. This research was carried out in order to test of different salinity levels effects on yield of barley (Hordeum Volgar L.) genotypes, in split plot experiment on the base of Randomized Completely Block Design with 3 replications. Salinity treatment involved 5 levels: S1 (control)=EC 4.5 ds/m, S2=EC 7.5 ds/m, S3=EC 10.5 ds/m, S4=EC 13.5 ds/m and S5=EC 16.5 ds/m as main plot and subplots were 9 genotype involved promising lines and varieties. The effect of salinity treatments studied by sampling on yield and tolerance indices, such as geometric mean productivity (GMP), stress susceptibility index (SSI), mean productivity (MP), stress tolerance index (STI), tolerance index (TOL) and yield reduction ratio (Yr). Result showed significant decrease in yield by increasing in salinity levels. The best performance belonged to ValFajr and MBS8715 genotypes, and MP, GMP and STI were determined as major and suitable indices for selecting cultivars with high yield under different levels of salinity stress and non- stress conditions.

Potato is considered as a strategic product in the food security of the country and is the fourth most consumed food product in Iran.  Due to its shallow rooting system, this plant is sensitive to water deficit.  In order to study the response of 20 potato genotypes to drought stress, a field experiment was conducted during 2018–2019 at the Seed and Plant Improvement Institute located at Karaj, Iran. The experimental design utilized was a Strip-plot based on randomized complete block design with three replications under two irrigation regimes (normal and stressed). ANOVA showed a significant difference for genotypes at 1% level for overall tuber yield, ware yield (tubers larger than 35 mm), seed yield (tubers between 35 and 55 mm), small yield (non-marketable potatoes), and marketable yield (total ware yield and seed yield). Eleven drought tolerance indices including STI, SSI, TOL, HARM, GMP, MP, YSI, DSI were calculated based on tuber yield under water deficit (Ys) and irrigated (Yp) conditions.  Our results showed a highly significant and positive correlation between MP, Yp and Ys.  The results of the analysis of PCA and the analysis of clustering showed that the drought-tolerance and drought-sensitive genotypes with the clustering pattern are consistent.  The MP, GMP, STI and MSTI identified 902027 genotypes as the best genotype under normal and stress conditions.  Among the genotypes and cultivars studied, 902027 and 8703- genotypes showed the highest MP and GMP, indicating high stability of genotypes in response to drought stress and thus can be considered as drought tolerant genotypes.

Cumin is one of the most important medicinal plants in Iran, which needs a lower irrigation to complete the growth stages. Therefore, cumin is one of the most valuable plants for cultivation in arid and semiarid regions of the world, especially in drought conditions. For this purpose, the present study was conducted to evaluate the key morphological and physiological parameters as well as the factors involved in oxidative stress and essential oil content in some ecotypes under drought stress and normal conditions. The experiment was arranged as factorial based on a completely randomized design with three replications and conducted in Saravan University's research greenhouse. Experimental factors included drought stress (stress and non-stress) and different ecotypes (eight ecotypes). The measured traits were plant height, number of secondary branches per plant, number of umbel per plant, number of umbellate per umbel, number of seeds per umbrel, 1000-seed weight and seed yield per plant, chlorophyll a, b and carotenoid content, and activity of biochemical factors (catalase, superoxide dismutase, peroxidase, malondialdehyde) and also seed essential oil. The results showed that drought stress reduced yield, yield components and photosynthetic pigments content. In general, Birjand ecotype had the highest grain yield per plant (1.37 g). Also, the activity of catalase, peroxidase and superoxide dismutase antioxidant enzymes was determined in this valuable medicinal plant. The drought stress increased the activity of these enzymes as well as the level of malondialdehyde, from 1.31 u/mgpro*min, 2.34 mg/g, 1.29 u/gFW and 21.87 µmol/gFW to 33.44, 4.37, 6.90 and 66.66, respectively. Finally, the tolerance of the studied ecotypes to drought stress was identified according to the measured indexes and Birjand ecotype was recognized as superior ecotype.

In order to evaluate drought tolerance of some safflower genotypes, an experiment was conducted at the Research Farm of Isfahan University of Technology in 2016 and 2017. In this study, 18 safflower genotypes selected from different local populations along with 2 exotic cultivars and one local population (21 genotypes) were separately evaluated at two normal (non-stress) and water deficit (stress) irrigation regimes, using a randomized complete block design with two replications. Drought tolerance and susceptible indices were calculated based on the seed yield. The results showed that there was significant differences among genotypes for seed yield. The genotypes M420 (4703 Kg/ha) and C116 (2723 Kg/ha) had the highest and lowest seed yield, respectively in normal irrigation condition, however, genotypes of A2 (2906 Kg/ha) and Arak2811 (1373 Kg/ha) had the highest and lowest seed yield, respectively in water deficit condition. Based on the correlation coefficients between indices and seed yield under both irrigation regimes, the indices of MP, GMP, STI, MpSTI and MsSTI were recognized as the best ones for identification of drought tolerant genotypes in safflower. The graphic biplot and cluster analysis indicated that genotypes M420, S149, K21, K12, E2428, E2417, AC-Stirling and A2 were more tolerant genotypes to water stress.

The evergreen tree olive (Olea europaea L.) is considered as one of the oldest plants cultivated in the Mediterranean basin. Drought is one of the most abiotic stresses that reduces olive yield in tropical and subtropical climates. Hence, identification of tolerant cultivars for cultivation in drought-prone areas is considered as one of important strategies in increasing cultivated areas for this plant. This study was aimed to investigate some of commercial cultivars and promising genotypes of olive using several yield-based drought tolerance and susceptibility indices.

To investigate the effect of drought stress on fruit yield and oil percentage in the 20 commercial cultivars and promising genotypes of olive, an factorial experiment based on randomized complete block with three replications was performed in Taroum Olive Research Station located in Zanjan province, during 2015-2017 cropping seasons. During the endocarp hardening period, drought treatments were applied based on cut of irrigation to the appearance of stress symptoms in the tree. Calculation of nine drought tolerance and susceptibility indices based on fruit yield and oil percentage under drought and normal irrigated conditions, correlations among indices and yields and principle component analysis based on correlation coefficient matric were followed.

Based on results, drought reduced fruit yield in all cultivars and genotypes, while it increased oil percentage in some of genotypes. Correlation coefficient analysis showed that all indices except TOL and SSI had significant positive relation with fruit yield and oil percentage under non-stress and drought stress conditions. The results of principal component analysis (PCA) showed that the first two components justified 98.78 and 99.59% of the total variation of fruit yield and oil percentage, respectively. The angles between indices in biplots rendered by PC1 and PC2 confirmed the results of correlation analysis. With respect to all three-dimensional graphs rendered by yields and STI index, promising genotype T7 placed in A group and it was selected as the most tolerant genotypes than others. Furthermore, this result was supported by the results of principal component analysis.

In general, our results revealed that the genotype T7 was identified as the most drought tolerant than other cultivars and genotypes. Thus, use of this genotype in breeding programs for improving tolerant of olive and also for cultivation in drought-prone environments is recommended. According to this results there was significant genetic diversity between studding genotypes that can be used in any improvement perspectives in the breeding projects.

Drought stress is one of the main problems in agriculture of Iran and the world. Among the environmental limiting factors of the yield crops, drought is the most important factor to reduce production, especially in arid and semi-arid regions. Drought stress reduces water content in plant tissues, lead to growth shrinkage and some physiological and metabolic changes in them. Food legumes, as one of the most important protein-rich vegetable sources, played a major role in providing human protein, especially in low-income and developing countries, and after cereals are the second most important source of human food. These plants, with bio-stabilization of nitrogen, provide a large portion of their nitrogen, and because they require low water and nutrients, they are highly desirable for cultivation in poor lands. Lentil (Lens culinaris Medik) is one of the beans that had more than 20% protein content and characteristics such as the ability to grow in inappropriate conditions and poor soils, has been able to play an important role in the low-income diet of people in developing countries. Regarding to the success of a breeding program depends on the size and diversity of genetic resources, genetic diversity lead to succeeding in selection, so identification of cultivars with high yield, as well as limiting factors of yield potential and genotypes tolerant to these factors in lentil seems to be necessary.

This research was carried out in the research farm of Ferdowsi University of Mashhad in 2014. In this experiment, 73 lentil genotypes including native genotypes and lines from other countries were cultivated in two separate plots under non stress and stress conditions in Augmented design. Five genotypes used as control (Kimia, Gachsaran, Cabralinta, ILL325 and ILL857). Controls were cultivated in all blocks. Before planting, field soil was sampled from a depth of 30 cm and pH values, organic matter, EC, macro elements (N, P and K) and soil texture were measured. The planting was carried out on March 20, 2014. At the same time, according to the fertilizer recommendation, the amount of required elements was added to the soil and immediately after cultivation, an irrigation step was conducted to ensure the emergence of all the seeds for both dry conditions (drought stress) and non-stress. Afterwards, irrigation was performed only for non-stress treatments and every 10 days.
 

The results showed that mean and standard deviation of lentil genotype yields under drought stress and non stress conditions revealed significant differences. Accordingly, the average yield of genotypes under conditions of stress was 20.4 g.m-2, which showed a decrease of 70.3% in non-stress conditions with 68.6 g.m-2. According to 147 mm rainfall from planting to harvest, this yield reduction was not expected, indicating the need for supplementary irrigation. High standard deviation between genotypes indicates a large variety of lentil genotypes, and this wide variety can be used as a valuable genetic resources for later studies. According to the results, there was a significant correlation between yield and stress (P≤0.01) (r=0.71**). Also, there was a positive and significant correlation between performance in non stress conditions with the old indices HARM, TOL, MP, STI, GMP, SSPI, ATI and the new SNPI index (P≤0.01), and the correlation between yield in non stress conditions and SSI and RDI were not significant. There was also a positive and significant correlation between performance in non-stress conditions and ATI, GMP, HARM, RDI, STI, SSI, TOL and MP, and the new SNPI index (P≤0.01), but between yield in non stress conditions and the SSI was a significant negative correlation (P≤0.01). Old indices of HARM, TOL, STI, GMP, MP, ATI, and two new indicators of SSPI and SNPI, all have a positive and significant correlation (p≤0.01) with performance under stress and non stress conditions and can be considered as suitable indicators for screening stress tolerant genotypes.
 

The results of current study showed that the new SNPI index, which has a very high correlation (99.9%) with yield in stress conditions, as well as the old indices of HARM, STI and GMP, which have the positive and significant correlation with each other and with performance in two. The conditions of non stress and stress have been identified as the most suitable and effective criteria for identifying and selecting genotypes tolerant to drought stress. The results obtained from the three-dimensional, biplot, and cluster analysis methods are in agreement with each other for selection of high yielding and drought tolerant lines. Accordingly, it seems that genotypes 40, 48, 71, 73, 3, 8 , 45 and 52 are the promising and proposing genotypes in the Mashhad climate for further studies